Question

Could I please get some clarification on a complex WCF service that exposes my business objects. Let’s say I have 4 objects: contact, organisation, project and letter.

Is the best way to create my service:

1. Make 4 contracts as ‘service objects’ and pass the object and the intended operation as values/parameters in the ‘service object’? or
2. Create contracts for all of the objects and their functions (which could be many)?

Many Thanks,

Chris

Answer 1

According to the Interface Segregation Principle, you might want to think about splitting those things up.

One typical approach is to have one interface (e.g. one “service”) per object type – e.g. one interface for Contact with all the operations needed and useful for contacts, etc.

Of course, you might also have methods that deal with multiple different types of objects – those are a bit tricky to place in a specific service contract.

Also, with WCF, you can easily have a single service implementation class that then in turn implements multiple of those interfaces at once – e.g. to use common code or common patterns.

But I guess it would be a good idea to rethink your service contract and convert it into smaller, more manageable chunks.

Update:

if your service implementation class implements four service contracts, then you’d have to configure it like this:

<services>
  <service name="YourNamespace.YourServiceImplementation">
     <host>
        <baseAddresses>
            <add baseAddress="http://YourServer/MyServices/" />
        </baseAddresses>
     </host>
     <endpoint name="Contact"
         address="Contact"
         binding="basicHttpBinding"
         contract="YourNamespace.IContactService" />
     <endpoint name="Letter"
         address="Letter"
         binding="basicHttpBinding"
         contract="YourNamespace.ILetterService" />
     <endpoint name="Organisation"
         address="Organisation"
         binding="basicHttpBinding"
         contract="YourNamespace.IOrganisationService" />
     <endpoint name="Project"
         address="Project"
         binding="basicHttpBinding"
         contract="YourNamespace.IProjectService" />
     <endpoint name="mex"
         address="mex"
         binding="mexHttpBinding" 
         contract="IMetadataExchange" />
  </service>
</services>

Now, each of your services is available at a specific endpoint:

• your IContractService is reachable at http://YourServer/MyServices/Contact
• your ILetterService is reachable at http://YourServer/MyServices/Letter

and so on….

For each of those addresses, you can now add service references from a client – add only those you really need. One app might need only a single of those services, another might need two or three etc.